<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>CSS 选择器</title>
    <style>
        * {
            font-size: 18px;
            font-weight: bold;
        }

        p {
            color: red;
        }

        .p2 {
            color: green;
        }

        #p3 {
            color: blue;
        }
    </style>
</head>

<body>
    <h1> this is the title </h1>
    <p> this is p text</p>
    <p class="p2"> this p2 text</p>
    <p id="p3">this p3 text</p>
    <a> this is a text</a>
</body>

</html>